Formation Of Interpenetrating Network Research Articles

Cellulosic supergel for oil and water dual absorption and remediation

An oil-water absorbing binate cellulosic supergel was developed for dual remediation of oil as well as water contamination. Scaffold for supergel was developed using high internal phase emulsion (HIPE) templating of an interpenetrating network of wood pulp cellulose (WPC) and hydroxyethyl cellulose (HEC) with polyacrylic acid (PAA). The HIPE was formed by dispersing dodecane in a continuous aqueous phase of WPC, HEC, and acrylic acid (AA) stabilized using sodium dodecyl sulfate (SDS). Micron-sized, interconnected pores were uniformly formed within the scaffold thereby achieving a remarkable porosity of 96.5 ± 4.8 % and a density of 0.054 ± 0.015 g/cm3. Combining emulsion templating with formation of inter-penetrating network (IPN) provided a unique approach to tailor pore size of the scaffold which unconventionally turned out to be smaller than the droplet size of the emulsion. The scaffold showed a significantly higher oil sorption value of 29.8 ± 2.9 g/g because of enhanced filling and trapping mechanism of oil in the porous structure of the scaffold. The scaffold showed persistent water or oil sorption for ten sorption-desorption cycles and successfully used to sorb both aqueous as well as oil media together thereby offering remediation for both in a single step from toxic wastes such as dyes.

Interpenetrating network based on soybean protein isolate and carboxymethyl chitosan: Investigation of intermolecular reaction mechanism, physicochemical stability and in vitro release properties of the hydrogel

In this study, interpenetrating network (IPN) hydrogels were constructed from soybean protein isolate (SPI) and carboxymethyl chitosan (CMCS) using TGase and genipin (GP) as cross-linking agents. And the influence of IPN formation on the physicochemical properties of hydrogels was illuminated. Multispectral analyses showed that there was a strong interaction between SPI and CMCS, which also promoted the increase of disulfide bonds and hydrophobic interactions in the hydrogels. The IPN was the densest when the addtion of SPI and CMCS were 10% and 3%, respectively. Meanwhile, this structure endowed the hydrogels with good mechanical properties and allowed them to exhibit thixotropy in rheological tests. The LF-NMR results showed that the IPN had a strong binding ability with water molecules and could effectively maintain the water in the hydrogel after freeze-thaw. Moreover, SPI-CMCS IPN hydrogels were pH responsive. This enabled it to adjust its own structure when pH changed, and to achieve controlled release of bioactives during simulated in vitro digestion. Overall, the results of this study showed that the IPN network formed by SPI and CMCS can effectively improve the performance of hydrogel. These results demonstrated the potential of SPI and CMCS as hydrogel synthesizers and provided a theoretical basis for the application of SPI-CMCS IPN hydrogel.

Simultaneous One-Pot Interpenetrating Network Formation to Expand 3D Processing Capabilities.

The incorporation of a secondary network into traditional single-network hydrogels can enhance mechanical properties, such as toughness and loading to failure. These features are important for many applications, including as biomedical materials; however, the processing of interpenetrating polymer network (IPN) hydrogels is often limited by their multistep fabrication procedures. Here, a one-pot scheme for the synthesis of biopolymer IPN hydrogels mediated by the simultaneous crosslinking of two independent networks with light, namely: i) free-radical crosslinking of methacrylate-modified hyaluronic acid (HA) to form the primary network and ii) thiol-ene crosslinking of norbornene-modified HA with thiolated guest-host assemblies of adamantane and β-cyclodextrin to form the secondary network, is reported. The mechanical properties of the IPN hydrogels are tuned by changing the network composition, with high water content (≈94%) hydrogels exhibiting excellent work of fracture, tensile strength, and low hysteresis. As proof-of-concept, the IPN hydrogels are implemented as low-viscosity Digital Light Processing resins to fabricate complex structures that recover shape upon loading, as well as in microfluidic devices to form deformable microparticles. Further, the IPNs are cytocompatible with cell adhesion dependent on the inclusion of adhesive peptides. Overall, the enhanced processing of these IPN hydrogels will expand their utility across applications.

Fundamental Concepts of Hydrogels: Synthesis, Properties, and Their Applications.

In the present review, we focused on the fundamental concepts of hydrogels—classification, the polymers involved, synthesis methods, types of hydrogels, properties, and applications of the hydrogel. Hydrogels can be synthesized from natural polymers, synthetic polymers, polymerizable synthetic monomers, and a combination of natural and synthetic polymers. Synthesis of hydrogels involves physical, chemical, and hybrid bonding. The bonding is formed via different routes, such as solution casting, solution mixing, bulk polymerization, free radical mechanism, radiation method, and interpenetrating network formation. The synthesized hydrogels have significant properties, such as mechanical strength, biocompatibility, biodegradability, swellability, and stimuli sensitivity. These properties are substantial for electrochemical and biomedical applications. Furthermore, this review emphasizes flexible and self-healable hydrogels as electrolytes for energy storage and energy conversion applications. Insufficient adhesiveness (less interfacial interaction) between electrodes and electrolytes and mechanical strength pose serious challenges, such as delamination of the supercapacitors, batteries, and solar cells. Owing to smart and aqueous hydrogels, robust mechanical strength, adhesiveness, stretchability, strain sensitivity, and self-healability are the critical factors that can identify the reliability and robustness of the energy storage and conversion devices. These devices are highly efficient and convenient for smart, light-weight, foldable electronics and modern pollution-free transportation in the current decade.

Structural characterization of interpenetrating network formation of high acyl gellan and maltodextrin gels

A mixed-gel of high acyl (HA) gellan gum and maltodextrin (MD) (potato DE2) demonstrated a range of physical properties with a proposed interpenetrating network. Mixed hydrocolloid gels allow for the development of novel properties that neither polymer alone could create allowing unique functionality in textures or controlled release. The aim of this work was to identify the type of network formation by examining material properties and the contribution from of each polymer. Material properties of quiescently set composite gels were characterized through bulk fracture, small deformation rheology, DSC, and microscopy. A continuous shift in fracture strain and modulus were created through mixed gels of the soft and flexible HA gellan with the firm and brittle MD. By adding MD (from 0 to 40%) at a constant 0.5% gellan, the gel true strain at fracture decreased from 0.50 to 0.18 while the Young's Modulus increased from 3 to 1780 kPa. No indication of phase separation or chemical complexation was measured. Analysis of the time-dependant MD contribution and composite material properties hypothesized a gelation mechanism in which HA gellan forms a network first and MD aggregates within the pores without phase separation. MD dominated the small deformation rheology while HA gellan appeared to dominate the fracture point. Material properties were indicative of the type of structural organization in the HA gellan MD mixed gel network.

A Bone Glue with Sustained Adhesion under Wet Conditions.

Bone glues often suffer from low adhesion to bone under wet conditions. This study aims to improve wet adhesiveness of a bone glue based on a photocurable poly(ethylene glycol) dimethacrylate matrix through in situ interpenetrating network formation by addition of six-armed isocyanate functional star-shaped prepolymers (NCO-sP(EO-stat-PO)). Biodegradable ceramic fillers are added to adjust the paste workability. The 3-point bending strength of the bone glues is in the range of 3.5-5.5 MPa and not significantly affected by the addition of NCO-sP(EO-stat-PO). Storage in phosphate buffered saline (PBS) decreases the bending strength of all formulations to approximately 1 MPa but the adhesion to cortical bone increases from 0.15-0.2 to 0.3-0.5 MPa after adding 20-40 wt% NCO-sP(EO-stat-PO) to the matrix. Bone glues without the NCO-sP(EO-stat-PO) additive lose their adhesiveness to bone after aging in PBS for 7 days, whereas modified glues maintain a shear strength of 0.18-0.25 MPa demonstrating the efficacy of the approach. Scanning electron microscopy and energy-dispersive X-ray spectroscopy investigations of the fracture surfaces prove a high amount of residual adhesive on the bone surface indicating that adhesion to the bone under wet conditions is stronger than cohesion.

Toughening improvement to a soybean meal-based bioadhesive using an interpenetrating acrylic emulsion network

The goal of this investigation was to improve the water resistance of soybean meal-based (SM) bioadhesive and enhance the mechanical properties of the bonded plywood by combining triglycidylamine (TGA) cross-linking with an acrylic emulsion interpenetrating network (IPN). The solid content, functional groups, crystallinity, mass loss after hydrolyzing, fracture surface micrographs, and thermal stability of the resulting adhesives were characterized. Three-ply plywood was fabricated and its dry and wet shear strength was determined. The experimental results indicated that the introduction of 8 % TGA produced an improvement of 15.1 % in the water resistance of SM adhesive and 86.8 % in the wet shear strength of plywood as a result of the chemical cross-linking between epoxy groups and protein molecules. However, this reaction increased the brittleness of adhesive and caused an insufficient dry bond strength. Incorporating 8 % AE into the SM/TGA adhesive resulted in a water resistance that was improved by 24.6 %, a dry shear strength that was increased by 44.0 % to 1.80 MPa and a wet shear strength that was increased by 47.9 % to 1.05 MPa. The improvements were attributed to the formation of IPN which increased the solid content, improved the toughness of the adhesive, and promoted an uniform and compact cured structure. All results suggested that chemical cross-linking can effectively improve the water resistance of SM adhesive, but will aggravate the brittleness. Toughening improvement is an effective approach to enhance the performance of the SPAs and solve the low dry strength issue of resulting composites.

Encapsulation of Lactococcus lactis subsp. lactis on alginate/pectin composite microbeads: Effect of matrix composition on bacterial survival and nisin release

Alginate/pectin hydrogel microspheres were prepared by extrusion based on a vibrating technology to encapsulate bacteriocin-producing lactic acid bacteria. Effects of both alginate/pectin (A/P) biopolymers ratio and physiological state of Lactococcus lactis subsp. lactis (exponential phase, stationary phase) were examined for nisin release properties, L. lactis survival and beads physico-chemical properties. Results showed that A/P composites were more efficient to increase beads properties than those formulated with pure alginate or pectin. Association of alginate and pectin induces synergistic effect which improves microbeads mechanical properties. FTIR spectroscopy confirms possible interactions between alginate and pectin during inter-penetrating network formation. Physiological state of bacteria during encapsulation process and microbeads composition (A/P ratio, enrichment of internal medium with nutrients) were determining factors for both bacteria viability and bacteriocin release. Of the several matrices tested A/P (75/25) with glucose-enriched M17 gave the best results when L. lactis was encapsulated in exponential state.

Epoxy–novolac interpenetrating network adhesive for bonding of plasma-nitrided titanium

This investigation highlights rationale to synthesize epoxy–novolac adhesive by novel interpenetrating network (IPN) technique. Physicochemical characteristics of the plain adhesive and IPN adhesive were carried out by Fourier transform infrared spectroscopy and thermal gravimetric analysis. Performing lap-shear test carried out plasma-nitrided titanium was fabricated with these adhesives and mechanical property of these adhesives. The blend of epoxy and novolac was optimized at 4:1 ratio, and the formation of IPN was confirmed by the suppression of creep with reference to neat epoxy and its swelling behavior. The adhesive with IPN shows significantly higher thermal stability than epoxy and leaves higher amount of residuals at the elevated temperature. Due to surface modification of titanium by plasma nitriding, wetting characteristics of titanium increases considerably and consequently, there was a significant increase in lap-shear strength adhesively of bonded titanium substrate.

Nanoscale structural and electronic evolution for increased efficiency in polymer solar cells monitored by electric scanning probe microscopy

Control of blend morphology at multi-scale is critical for optimizing the power conversion efficiency (PCE) of plastic solar cells. To better understand the physics of photoactive layer in the organic photovoltaic devices, it is necessary to gain understanding of morphology and the corresponding electronic property. Herein we report the correlation between nanoscale structural, electric properties of bulk heterojunction (BHJ) solar cells and the annealing-induced PCE change. We demonstrate that the PCE of BHJ solar cells are dramatically improved (from 1.3 % to 4.6 %) by thermal annealing, which results from P3HT crystalline stacking and the PCBM aggregation for interpenetrated network. The similar trend for annealing-induced photovoltage and PCE evolution present as an initial increase followed by a decrease with the annealing time and temperature. The surface roughness increase slowly and then abruptly after the same inflection points observed for photovoltage and PCE. The phase images in electric force microscopy indicate the optimized P3HT and PCBM crystallization for interpenetrating network formation considering the spectroscopic results as well. From the correlation between surface photovoltage, blend morphology, and PCE, we propose a model to illustrate the film structure and its evolution under different annealing conditions. This work would benefit the better design and optimization of the morphology and local electric properties of solar cell active layers for improved PCE.

Development and evaluation of pH-dependent interpenetrating network of acrylic acid/polyvinyl alcohol

The objective of the present work was to synthesize interpenetrating networks (IPNs) of acrylic acid/polyvinyl alcohol (AA/PVA) by free radical polymerization using N,N-methylenebisacrylamide (MBAAm) and glutaraldehyde as cross-linkers. The IPNs were evaluated for swelling, diffusion coefficient and network parameters by using Flory–Huggins theory, i.e., the average molecular weight between cross-links (M c), polymer volume fraction in swollen state (V 2,s), number of repeating units between cross-links (M r) and cross-linking density (N). It was found that the degree of swelling of AA/PVA interpenetrating network increases greatly within the pH range 5–7 depending on composition. The gel fraction and porosity increased by increasing the concentration of AA or PVA, while by increasing the degree of cross-linking, porosity decreased and gel fraction increased. Selected samples were loaded with chlorpheniramine maleate as a model drug. Drug release was studied in USP, hydrochloric acid buffer solution of pH 1.2 and phosphate buffer solutions of pH 5.5 and 7.5. Drug release data were fitted into various kinetics models, e.g., zero-order, first-order, Higuchi and Peppas models. The results of the kinetics investigation showed that the drug release from IPNs followed non-Fickian diffusion. Fourier transform infrared spectra confirmed the formation of cross-linked IPNs as there was a shifting to lower frequency of 1,713–1,718 cm−1 with reduced intensity, while scanning electron microscopy revealed uniform distribution of drug in IPNs.

Viscoelastic behavior of NBR/phenolic compounds

NBR/phenolic interpenetrating networks (IPNs) offer a wide variety of mechanical and physical properties at moderately high temperature. This temperature stability along with oil and fuel resistance property has made IPNs appropriate candidates for various applications. In the present work, NBR compounds containing 5, 7 and 12 phr of Novolac, as a curable phenolic resin was formulated using a two-roll mill. Low and high acrylonitrile NBR; KNB 35L and Europrene N4560 were selected in the compound and the same condition of mixing was applied in the blend preparation stage. Curing test, followed by a cooling period and the stress relaxation test were carried out consecutively and automatically in a rubber process analyzer. The samples presented various relaxation times. The relaxation curves were well estimated by Maxwell model and the Prony coefficients were determined. Furthermore, compression test was performed on the samples, so that the set or permanent deformation of each sample was measured. The results of both tests have indicated that by adding phenolic resin into the NBR matrices, the viscoelastic behavior of the compounds become more elastic, to the detriment of the viscous component. This phenomenon would be due to IPN formation in the compounds. In addition, by increasing the phenolic resin content in the compounds, the difference between maximum and minimum torque (M H − M L) value became greater, which is an indicator of higher cross-link density and IPN formation. Swelling test results confirmed more extensive cross-links in the compounds by addition of more resin into the compound.

Polyaniline-poly(vinyl alcohol) IPN-composite prepared from potassium dichromate embedded PVA film: a material for humidity sensing application

Polyaniline-polyvinyl alcohol (PANI-PVA) interpenetrating network composite film is successfully prepared by in situ polymerization of aniline within PVA film embedded with different concentrations of potassium dichromate (K2Cr2O7). The resulted composite is characterized by UV-Visible spectroscopy, SEM and XRD, TGA techniques and confirmed the formation of interpenetrating network formation of PANI within PVA matrix. Electrical conductivity of the composite films increase from 10−6 to 10−2 S/cm with the increase in the loading of dichromate from 10−4 to 10−2M. Further, exposing in humidity environment, the conductivity of the composite films increases from 14 to 100% with the increase in humidity conditions from 11.3 to 84.3%.

Interpenetrating network hydrogel membranes of sodium alginate and poly(vinyl alcohol) for controlled release of prazosin hydrochloride through skin

Interpenetrating network (IPN) hydrogel membranes of sodium alginate (SA) and poly(vinyl alcohol) (PVA) were prepared by solvent casting method for transdermal delivery of an anti-hypertensive drug, prazosin hydrochloride. The prepared membranes were thin, flexible and smooth. The X-ray diffraction studies indicated the amorphous dispersion of drug in the membranes. Differential scanning calorimetric analysis confirmed the IPN formation and suggests that the membrane stiffness increases with increased concentration of glutaraldehyde (GA) in the membranes. All the membranes were permeable to water vapors depending upon the extent of cross-linking. The in vitro drug release study was performed through excised rat abdominal skin; drug release depends on the concentrations of GA in membranes. The IPN membranes extended drug release up to 24 h, while SA and PVA membranes discharged the drug quickly. The primary skin irritation and skin histopathology study indicated that the prepared IPN membranes were less irritant and safe for skin application.

Preparation and characterization of epoxidate poly(1,2‐butadiene)–toughened diglycidyl ether bisphenol‐A epoxy composites

AbstractBy the oxidation of liquid poly(1,2‐butadiene) (LPB) with H2O2/HCOOH, epoxidate poly(1,2‐butadiene) (ELPB) was obtained as a toughening agent to prepare diglycidyl ether bisphenol‐A (DGEBA) epoxy composites by using V115 polyamide(PA) as a cross‐linking agent. DGEBA, ELPB, and the composites were effectively cured by PA at 100°C for 2 h followed by postcuring at 170°C for 1 h. Thermal gravimetric analysis results in air and nitrogen atmosphere showed that the thermal stability of composites could be improved by the addition of ELPB. Compared with DGEBA/PA, the composites exhibited a decrease in strength at yield but an increase in strain at break with the increase in ELPB amount. The composite with 10% ELPB exhibited both thermal stability and tenacity superior to those of DGEBA/PA and composites with 5 and 20% ELPB, respectively. The improvements in thermal and mechanical properties of composites depended on the formation of Inter Penetrating Networks (IPN) among DGEBA/PA/ELPB and their distributions in the matrix. At an appropriate ELPB amount, the IPN, mostly made of DGEBA/PA/ELPB, may be distributed more evenly in the matrix; less ELPB resulted in the formation of IPN mainly made of DGEBA/PA; excessive addition of ELPB resulted in the local aggregation of ELPB/PA and phase separations. The toughening mechanism was changed from chemically forming IPN made of DGEBA/PA/ELPB to physically reinforcing DGEBA/PA by ELPB/PA with the increase in ELPB addition. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of high-pressure homogenization on droplet size distribution and rheological properties of ice cream mixes

The effect of different homogenization pressures (15/3MPa and 97/3MPa) on fat globule size and distribution as well as on structure-property relationships of ice cream mixes was investigated. Dynamic light scattering, steady shear, and dynamic rheological analyses were performed on mixes with different fat contents (5 and 8%) and different aging times (4 and 20h). The homogenization of ice cream mixes determined a change from bimodal to monomodal particle size distributions and a reduction in the mean particle diameter. Mean fat globule diameters were reduced at higher pressure, but the homogenization effect on size reduction was less marked with the highest fat content. The rheological behavior of mixes was influenced by both the dispersed and the continuous phases. Higher fat contents caused greater viscosity and dynamic moduli. The lower homogenization pressure (15/3MPa) mainly affected the dispersed phase and resulted in a more pronounced viscosity reduction in the higher fat content mixes. High-pressure homogenization (97/3MPa) greatly enhanced the viscoelastic properties and the apparent viscosity. Rheological results indicated that unhomogenized and 15/3MPa homogenized mixes behaved as weak gels. The 97/3MPa treatment led to stronger gels, perhaps as the overall result of a network rearrangement or interpenetrating network formation, and the fat globules were found to behave as interactive fillers. High-pressure homogenization determined the apparent viscosity of 5% fat to be comparable to that of 8% fat unhomogenized mix.

Synthesis, characterization, and anticorrosive coating properties of waterborne interpenetrating polymer network based on epoxy‐acrylic‐oleic acid with butylated melamine formaldehyde

AbstractThe present study reports the synthesis and characterization of waterborne interpenetrating network (IPN) of epoxy‐acrylic‐oleic acid (EpAcO) with butylated melamine formaldehyde (BMF). The effect of BMF on the formation of IPN was investigated in terms of physicochemical, spectral, morphological, and thermal analyses. The coating properties of the IPN were investigated for their physicomechanical, corrosion resistance, and antimicrobial activity. The formation of the IPN was confirmed by FTIR and 1H NMR analyses as well as physicochemical properties. The EpAcO‐BMF IPN coatings were found to exhibit far superior corrosion resistance performance and good thermal stability when compared with the reported waterborne epoxy acrylic‐melamine formaldehyde systems [EpAc‐MF]. The preliminary antimicrobial investigations of the IPNs were carried out by agar diffusion method against some bacteria and fungi. The results revealed that antimicrobial activities were enhanced upon the formation of IPN. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Trends - the future belongs to hybrid thermosets

mostly due to their ‘blending’. Via ‘blending, alloying’ the beneficial properties of the related thermoplastic resins can be combined and even tailored upon request in many cases. Blending does not necessary mean melt compounding, but covers numerous other techniques, as well (e.g. ‘reactor blends’ produced by in-situ polymerization). Interestingly, fewer efforts were dedicated to follow this concept for thermosets, except rubbers. Similar to thermoplastic systems, the ‘blending concept’ was introduced for thermosets when starting with their toughening. Nowadays, toughened thermosets, especially epoxy resins, are commercialized. Their toughener content is usually less than 10 wt.%. The vivid academic interest in the past to prepare interpenetrating network (IPN) structured systems can be considered as the beginning of thermoset ‘hybridization’. Combination of two or more resins, which crosslink separately or co crosslink with each other in various extents, means a great potential for property modification. A commercial breakthrough with this concept was already achieved with unsaturated polyester-urethane and vinylester-urethane hybrid resins. The driving force of resin hybridization in the future is linked with the necessary use of resins made (at least partly) from renewable resources. Note that the crosslinked network of resins of natural origin (e.g. from plant oils which will come sooner or later from gene-manipulated plants) can never be so tight as that of ‘traditional’ ones derived from petrochemical resources. This is due to the fact that the molecular segments between the crosslinking sites are much longer (and at the same time usually less reactive) than in the present systems. So, the related products are closer to rubbers than to thermosets which is well reflected by their low glass transition temperature (Tg). Consequently, additional co reactions and/or formation of IPN or IPN-like structures are needed to push the stiffness, strength and Tg toward higher values. It can be prophesied that the polyurethane chemistry will be one of the right tools to reach this target due to its versatility. However, we are faced with severe problems when following resin hybridization routes, from which only one has to be borne in mind here. The end-users prefer to utilize 1or (maximum) 2-component systems, which can not always fulfilled by hybrids. To develop ‘userfriendly’, robust 2-component systems is a great challenge that can likely be met by adopting suitable blocking, end capping strategies. So, there is much to do, but it is of worth, is not it?

Novel interpenetrating network chitosan-poly(ethylene oxide- g-acrylamide) hydrogel microspheres for the controlled release of capecitabine

This paper describes the synthesis of capecitabine-loaded semi-interpenetrating network hydrogel microspheres of chitosan-poly(ethylene oxide- g-acrylamide) by emulsion crosslinking using glutaraldehyde. Poly(ethylene oxide) was grafted with polyacrylamide by free radical polymerization using ceric ammonium nitrate as a redox initiator. Capecitabine, an anticancer drug, was successfully loaded into microspheres by changing experimental variables such as grafting ratio of the graft copolymer, ratio of the graft copolymer to chitosan, amount of crosslinking agent and percentage of drug loading in order to optimize process variables on drug encapsulation efficiency, release rates, size and morphology of the microspheres. A 2 4 full factorial design was employed to evaluate the combined effect of selected independent variables on percentage of drug release at 5 h (response). Regression models were used for the response and data were compared statistically using the analysis of variance (ANOVA). Grafting, interpenetrating network formation and chemical stability of the capecitabine after encapsulation into microspheres was confirmed by Fourier infrared spectra (FTIR). Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) studies were made on drug-loaded microspheres to investigate the crystalline nature of drug after encapsulation. Results indicated amorphous dispersion of capecitabine in the polymer matrix. Scanning electron microscope (SEM) confirmed spherical shapes and smooth surface morphology of the microspheres. Mean particle size of the microspheres as measured by the laser light scattering technique ranged between 82 and 168 μm. Capecitabine was successfully encapsulated into semi-IPN microspheres and percentage of encapsulation efficiency varied from 79 to 87. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) until complete dissolution. The release of capecitabine was continued up to 10 h. Release data were fitted to an empirical relationship to estimate the transport parameters. Dynamic swelling studies were performed in the simulated intestinal fluid and diffusion coefficients were calculated by considering the spherical geometry of the matrices.

Influence of the process on phase separation induced by radical copolymerization of styrene and divinylbenzene in the presence of reactive polyurethane network precursors

AbstractInterpenetrating polymer systems based on crosslinked polyurethane (PU) and polystyrene (PS) were prepared at room temperature by a one‐shot (in situ) method, starting from an initial homogeneous mixture of reagents via noninterfering mechanisms. Both polymerizations were performed either simultaneously or one after the other. True simultaneity at every stages of the process is not possible. Despite the difference in refractive index of the components, hazy or optically clear films were obtained, thus indicating various levels of phase separation, also confirmed by glass transition temperature (Tg) measurements. The results suggest that controlling the chemistry and process (crosslink density, composition, and time sequence of events) of in situ interpenetrating network formation will give various morphologies, and hence properties, ranging from microphase separated materials to larger macrophase separated materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006